Electric switch



Patented Jan. 20, 1953 Y ELECTRIC SWITGH William E. Engelhard,` North Arlington, N. J.

Application January 17, 195,1, Serial No. 206,367-

3 Claims.

This invention relates to electric switches such as are used for the control of circuits or power sources for electrically actuated apparatus, such as, for example, electric furnaces and the like. The current through such switches in some cases is passed through a valve, such as a vacuum tube, photo-electric cell, or the like, the output of which in turn is affected by changes in temperature or other variable condition. For example, it is old in the art to provide a mechanism for the control of an electric furnace wherein, when the temperature in the furnace builds up to a pre-v determined value, an apparatus will be actuated responsive to said temperature rise to open the furnace circuit.

--'An apparatus of the type above referred to is exemplified in my application for Switch Gontrol Device executed simultaneously herewith and lled January 1'7, 1951, Serial No. 206,366; and wherein the reference characters 3|, 32 indicate the mechanism affected by change in temperature or other condition and the reference character 4G designates a valve through which the current ows to the switch 4 2 in the circuit of the furnace or other mechanism to be controlled. In said application, I have disclosed a form of switch control device which is designed to modify the conventional mechanism above re-v ferred to, as will become apparent from a con-r sideration of the drawings and description of said application.

t The present application is broadlyl designed to provide a means for accelerating the moment of' opening of the control switch which, in the draw. ing'sof this application, is designated by the ref--A erence character lil, responsive to a r-ise in temperature or other condition toward the prede,- termined value, and to automatically accelerate the moment of closing said control switch responsive to the fall of the temperature or other condition below the predetermined value. For eX- ample, the invention is adapted to control the objectl I2 which may be ther4 heatingunit ofa furnace so as to actuate the same only when the temperature thereof falls, belQW a Certain point. It is desirable,y in many cases, to adhere quite. closely t9 predetermined, temperature `for best 'Qpereiira The present investiga Dravid@ all automatic central. v vhith will. cui Qf; the liegt,-

'ile mit for example. just` es the temlrature is about to reach the predetermined point, at th same time guarding against too great a drop by turning the same on again as soon as the temperature drops only suicient to be just past the desired point-in other words, to turn it on again as the temperature returns to the desired point.

The invention obviously also embraces the reverse arrangementclosing the control switchrespcnsive to an approach to the desired or pre-V determined condition and opening it on depar ture therefrom. The specific application of the invention to meet the requirements of the job at hand will be obvious from a consideration of theV description below and the accompanying drawing which villustrate 'one of several possible practical embodiments of the invention which will become apparent tol those skilled i'n this art from the present disclosure.

In the drawings:

The ligure represents a schematic wiring diagram of a mechanism embodying the invention.

As shown in the drawings, the switch mechanism of the present invention comprises an electro-magnetic control switch I0, actuated by: an electro-magnetic coil whose ends are connected to taps 2|, 2l wired to the circuit II. When current from circuit II is passed through the control switch I0 of sufficient value to set up an electro-magnetic eld to actuate the said switch, the switch will close the circuit I9, 20. But when the currentthrough circuit I I is of less than said predetermined value, the electro-magnetic iield will be inadequate for the purpose mentioned and the switch will open, breaking the circuit I9, 20;

Pursuant to the instantinvention, a coil I3 is juxtaposed in the area of the electro'emagnetic iield which actuates the switch I0, and a thermo-L couple bar I4 is connected at its ends I5, I6 to saidcoil I3. Heater elements I5a, IBa, juxtaposed relative to said bar ends for heatingV said ends, are connected selectivelybyswitch I1' to a heat source indicated generally at 2-2. Said heat source 2-2v mayl be a heat transformer power source of anyI desired or-convenient, construction or the like for selective connection through the heater switch I'I to theY heater element contacts i511, -I-Eb. The switch Il is movable to op.. erative position on ene ofv the contacts.- Ilb, IBb, leadingto the heater coils I5'a, Ita selectively responsive to maintenancel of; the value, of cur.-

rent in circuit II sufl'icient to actuate the switch I1, and to the other operative position on the other contact when the current falls below that value.

Thus, in one operative position of the heater switch I'I, a heater element will be actuated to heat the adjacent end of the thermo-couple bar I4 to pass a current through coil I3 in a direction which will oppose the operative electro-magnetic field of the coil of switch I connected to the taps 2|, 2|'. This will have the effect of accelerating the moment of opening of switch I0 by accelerating the moment when the current flowing therethrough will be inadequate to actuate the same. The drop in current, opening switch I0, will actuate switch I'I to its other operative position, sending current through coil I3 in a direction to assist the operative electro-magnetic field of the switch I0 so that, when the current from circuit I I flowing through the coil connected to taps 2 I, 2| approaches the moment of attaining the predetermined value, the switch I0 will operate in advance of and in anticipation of said moment.

The operation above described is repeated responsive to the current conditions of circuit I I which, in turn, is controlled by the condition responsive valve 26 between circuit II and power source 25, the valve 26 being connected to the object I2 as indicated at 21 and modifying the value of current II responsive to the condition of object I2. The apparatus is accordingly effective to anticipate the moments of normal opening and closing action of control switch Ill and to thus open the switch and close the switch sooner than would normally occur.

Control switches such as switch I 0 are used, for example, to control temperatures and other conditions which, in accordance with the law of inertia, continue in a given direction for at least a short period of time after starting to move in the direction. The mechanism described anticipates this inertia effect to smooth out or modulate the action so as to make the same less abrupt, by an automatic switch mechanism of maximum practical utility.

The value of the electro-magnetic field set up in coil I3 by the heating of thermo-couple bar I4 is only a fraction of the value of the electromagnetic ileld set up in the operative coil connected to taps 2|, 2| of switch I0. Thus, the coil I3 adds to or subtracts from the value of the coil of switch I0 connected to taps 2 I, 2| according to the direction of flow of current through coil I3, which in turn depends on which end of the thermo-couple bar I4 is being heated.

The control switches I0 and I'I shown in the drawings are of the well-known relay type utilizing an electro-magnetic coil to actuate the same. Other electro-magnetic mechanisms, such as solenoids, etc., may be used; in fact, the switch I0 may be any mechanism the operation of which will be affected by the electro-magnetic field set up by coil I3 pursuant to the invention. The illustration in the drawings of control switches I0 and I'I are simply by way of example. It will likewise be understood that the heater coils Ia, IBa and the heater source 22 may be varied, other heating elements being effective to the same end. The design of the thermo-couple bar I4 might be varied to any other form useful for the indicated purpose. If desired, the heater elements, instead of being adjacent the thermo-couple bar -I4, might be directly wound thereon or formed unitarily therewith. The recitation of heater '4 elements in the claims or other parts of this application shall be deemed to include heater elements juxtaposed adjacent the bar I4, or wound thereon, or formed unitarily therewith, or otherwise disposed for the purpose mentioned.

It will be apparent from the foregoing description that the mechanism is operative for the purpose mentioned without regard to the specific agent or means causing the current in circuit II to uctuate. As above described, by way of illustration only of one of many possible practical forms of the invention, a valve 26 connected to the object to be controlled I2 may be responsible for the uctuations of current in circuit I I. The valve 26 may, for example, be a vacuum tube having a grid or other -current modifying part 29 affecting the value of current output from valve 26, the grid 29 in turn responding to the condition of object I2 as by connecting the grid 29 with a thermo-couple 28 or the like at object I2.

The thermo-couple bar I4 may be made in any suitable, desired or convenient proportions and outline. It may be positioned in a relatively heavy metallic block 30 which is slotted to receive the same medially intermediate the ends I5, I6 thereof and which will serve as a heat reservoir or storage element, absorbing heat from either heater coils I5a or IGa. The block 30 serves to direct the thermo-electric currents either to the right or to the left, in dependence upon the energization of heater coils |511J or ISa, respectively, the direction of which currents controls the aiding or bucking electro-magnetic effects produced by the coil I3. The device is not affected by room temperature changes, containing as it does the opposed units Ia, Ifia, which will neutralize the effect of such changes.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1. A control system for making and breaking the electrical circuit to a device experiencing iiuctuations in energy level, which comprises a main switch, an electromagnet for controlling said switch, a current supply connected to said electromagnet for operating said electromagnet in response to a predetermined intensity of current, an auxiliary magnetic coil disposed in the induction field of said electromagnet in bucking or aiding relation thereto in dependence upon the direction of current oW through said coil, a thermocouple having the opposite ends thereof connected to the opposite ends of said magnetic coil, alternately operated heating device in proximity to the opposite ends of said thermocouple to alternately control the direction of current flow through said thermocouple and magnetic coil and thereby to selectively buck or aid the induction effect of said electromagnet, and a relay switch connected to the current supply for said electromagnet adapted to energize the one of said heating devices which gives rise to said bucking induction effect when the electromagnet is supplied by the more intense current and the other of said heating devices which gives rise to said aiding induction eifect when the electromagnet is supplied by the less intense current, whereby said auxiliary magnetic coil accelerates the action of said electromagnet in its alternate control of said main switch.

2. An apparatus as set forth in claim 1 wherein said thermocouple is in the form of a bar with a heavy metallic block at the mid-portion thereof.

3. An apparatus as set forth in claim 1 wherein said heating devices having a common junction point, and said relay switch comprises an electromagnetic coil and a movable armature controlled thereby, an electrical connection from said armature to the common junction point of the heating devices in proximity to said thermocouple including an energy translating device, and a xed contact on each side of said armature connected to the opposite free ends of said heating devices and adapted to selectively complete an electrical circuit through said armature, one heating device and energy translating device to selectively heat one side of said thermocouple and thereby to energize the auxiliary magnetic coil in the desired sense.

WILLIAM E. ENGELHARD.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,685,995 Gano Oct. 2, 1928 2,139,504 King Dec. 6, 1938 2,215,067 Denison Sept. 17, 1940 2,265,294 Lange Dec. 9, 1941 2,351,277 Mantz June 13, 1944 2,409,492 Jones Oct. 15, 1946 2,446,216 Dodd Aug. 3, 1948 

